Automatic regulating valve apparatus

ABSTRACT

An automatic regulating valve apparatus comprises a main valve unit, and a pilot valve unit operatively connected to the main valve unit to control the main valve unit. The main valve unit comprises a main valve casing, a main valve element disposed in the main valve casing, and a main valve driving member disposed in the main valve casing together with the main valve element and having a pressure receiving area greater than that of the main valve element, the main valve element is disposed on the upstream side of a valve seat so as to form a restricting passage between the main valve element and the main valve seat, and the main valve driving member is disposed for sliding movement in a space defined by a cylindrical wall formed in the main valve casing so as to define a main valve driving pressure chamber together with the cylindrical wall. The pilot valve unit comprises pilot valves A and B which are operated for opening and closing operations according to the variation of a pressure difference across an orifice included in the main valve unit, a pressure difference across the main valve unit, liquid level on the downstream side of the main valve unit or the pressure on the upstream side of the main valve unit. The pilot valve A and the pilot valve B are arranged in series and connected between the upstream and the downstream side of the main valve unit by connecting passages with a chamber between the pilot valves A and B connected to the main valve driving pressure chamber. The pressure in the main valve driving pressure chamber is varied by the coordinated operations of the pilot valves A and B to regulate the opening of the main valve unit. Thus, the automatic regulating valve apparatus  4  exercises automatic control functions including a constant-flow control function, an emergency shutoff function, a liquid level control function and an upstream pressure control function.

TECHNICAL FIELD

The present invention relates to an automatic regulating valve apparatusto be installed in a fluid conducting line. More specifically, thepresent invention relates to an automatic regulating valve apparatuswith a pilot valve unit based on a novel technical idea, capable ofbeing easily formed in large size or high-pressure type, and ofexercising excellent automatic control functions including aconstant-flow control function, an emergency shutoff function, a liquidlevel control function and an upstream pressure control function, havinga perfect sealing function and a clogging preventing function achievedby a self-cleaning operation, and convenient for application.

In this description, the terms “water” and “liquid” are used as generaldesignations of fluids.

BACKGROUND ART

Various kinds of automatic regulating valve devices have been proposed.A lift valve apparatus disclosed in JP-B No. 2-46818 is a direct-actingconstant-flow valve not provided with any pilot valve.

As shown in FIG. 23, this prior art lift valve apparatus has a valvecasing 101 having an internal space divided into three passages, i.e.,an inlet passage a an intermediate chamber u and an outlet passage carranged in that order from an upstream side toward the downstream side,by a flow rate setting valve element 103 and an automatic restrictioncontrol valve element 104. The respective pressure receiving areas ofthe valve element 103 and the automatic valve element 104 aresubstantially equal. A sealed chamber e defined by a sealing member 104sattached to the automatic valve element 104, and a valve top 102 isconnected to the inlet passage a by a connecting passage t. Theautomatic valve element 104 is biased for automatic restriction controlfunction by a balancing spring 105. The automatic valve element 104moves automatically in opposite directions according to the position ofthe valve element 103 corresponding to a set opening to maintain aconstant flow rate.

This direct-acting constant-flow valve is used prevalently. However, thedirect-acting constant-flow valve has unsolved problems in forming thesame in large size and high-pressure type. The size of the balancingspring 105 increases inevitably as the size and the pressure capacity ofthe direct-acting constant-flow valve are increased, entailingdifficulties in assembling, designing and manufacturing thedirect-acting constant-flow valve. It is not easy to select a balancingspring 105 capable of properly controlling flow rate in a conduit inwhich pressure varies frequently.

Pilot-operated automatic regulating valve apparatuss provided with amain valve driving piston or diaphragm operated by a pilot valve, whichadjusts flow rate with a fixed restriction passage such as a needlevalve, are also used prevalently instead of the direct-actingconstant-flow valve. A liquid level control valve provided with a floatvalve as a pilot is one of those valve apparatuses.

Referring to FIG. 24, this liquid level regulating or control valveapparatus has a main valve unit controlled by the opening and closingactions of a piloting float valve 230. The main valve unit has a mainvalve casing 201, a main valve element 205 disposed in the main valvecasing 201, and a main valve driving member 206 having a pressurereceiving area greater than that of the main valve element 205 andcombined with the main valve element 205. A restricted passage is formedbetween the main valve element 205 and a main valve seat 204. The mainvalve driving member 206 is fitted slidably in a space defined by acylindrical wall 203 formed inside the main valve casing to form a mainvalve driving pressure chamber d between the cylindrical wall 203 and avalve top 202. The float valve 230 closes when the liquid level on thedownstream side of the main valve unit rises above a predetermined leveland opens when the same drops below the predetermined level. The mainvalve driving pressure chamber d is connected to an inlet passage in anupstream end of the main valve unit by a connecting passage t providedwith a fixed restricting valve 220 and is connected through the floatvalve 230 to the downstream side of the main valve unit. The pressure inthe main valve driving pressure chamber d drops to the pressure in apassage on the downstream side of the main valve unit when the floatvalve 230 opens, and the main valve element 205 is moved in a valveopening direction to start supplying the liquid. In the meantime, thefloat valve 230 closes when the liquid level on the downstream side ofthe main valve unit rises above the predetermined level, the pressure inthe main valve driving pressure chamber d rises to the pressure on theupstream side of the main valve unit, and the main valve element 205 ismoved so that a sealing member 205 s comes into close contact with themain valve seat 204 to stop supplying the liquid.

This prior art pilot-operated automatic regulating valve apparatus,however, needs troublesome maintenance and management work and has manyproblems in durability. The following are examples of those problems.

(1) Most of various sealing means for use as a sealing member 206 s puton the main valve driving member 206 in contact with the cylindricalwall 203 are required to achieve perfect sealing not permitting leakagewhen the main valve unit is closed, and a bellows and a diaphragm havebeen employed as the sealing member 206 s to solve the problem. When thepilot-operated automatic regulating valve apparatus is of a large sizeand a large pressure capacity, difficulties arise in the durability andmachining accuracy of the sealing arrangement, and troublesomemaintenance and management work is necessary; that is, the fluid isliable to leak downstream.

(2) The main valve unit must gradually be driven to prevent undesirableoperations, such as chattering and hunting, due to pressure pulsationresulting from the change of flow. Therefore, the prior artpilot-operated automatic regulating valve apparatus needs the fixedrestricting valve 220 forming a restricted passage, such as a needlevalve, in the connecting passage t through which the fluid of theupstream pressure flows. This small restricted passage is clogged withsand and dust to cause troubles and hence a strainer or the like isnecessary. Thus, it is difficult to use this prior art pilot-operatedautomatic regulating valve apparatus in fluid passages other than afluid passage for a clean liquid.

The present invention employs a pilot valve unit based on a noveltechnical idea to realize a valve capable of being formed in a largesize and a large pressure capacity, which could not have been realizedby the prior art direct-acting constant-flow valve. Also, it is anobject of the present invention to provide a pilot-operated automaticregulating valve apparatus capable of exercising excellent automaticcontrol functions including a constant-flow control function, anemergency shutoff function, a liquid level control function and anupstream pressure control function, having a perfect sealing function,provided with a pilot valve unit not having any fixed restrictingpassage, such as a needle valve, and capable of exercising a cloggingpreventing function achieved by self-cleaning operation, capable ofoperating quickly without entailing chattering and hunting, andconvenient for application.

DISCLOSURE OF THE INVENTION

With the foregoing object in view, the present invention provides anautomatic regulating valve apparatus comprising a main valve unit and apilot valve unit operatively connected to the main valve unit to controlthe main valve unit, wherein the main valve unit comprises a main valvecasing, a main valve element disposed in the main valve casing, and amain valve driving member disposed in the main valve casing togetherwith the main valve element and having a pressure receiving area greaterthan that of the main valve element, the main valve element is disposedon an upstream side of a valve seat so as to form a restricting passagebetween the main valve element and the main valve seat, the main valvedriving member is disposed for sliding movement in a space defined by acylindrical wall formed in the main valve casing so as to define a mainvalve driving pressure chamber together with the cylindrical wall, arestrictor is disposed in a passage extending through the main valveunit, the pilot valve unit comprises a pilot valve A and a pilot valve Bwhich are operated by a balance of counteracting forces respectivelyproduced by pressure difference across the restrictor and afixed-pressure applying means, the pilot valve A opens when the pressuredifference across the restrictor rises above a predetermined level andcloses when the same drops below the predetermined level, the pilotvalve B closes when the pressure difference across the restrictor risesabove the predetermined level and opens when the same drops below thepredetermined level, and the pilot valve A and the pilot valve B arearranged in series and connected between the upstream and the downstreamside of the main valve unit by connecting passages with a chamberbetween the pilot valves A and B connected to the main valve drivingpressure chamber.

The restrictor may be of a variable type.

The automatic regulating valve apparatus may further comprise a valvemeans placed in series in a connecting passage connected to the pilotvalve B to open and close the connecting passage.

The automatic regulating valve apparatus may further comprise a valvemeans placed in series in the connecting passage connected to the pilotvalve B to close the connecting passage when an abnormal conditiondetecting means detects an abnormal condition.

The automatic regulating valve apparatus may further comprise a valvemeans capable of closing when liquid level on the downstream side of themain valve unit rises above a predetermined level and of opening whenthe same drops below the predetermined level, and placed in series in aconnecting passage connected to the pilot valve B.

The automatic regulating valve apparatus may further comprise a valvemeans capable of closing when the liquid level on the downstream side ofthe main valve unit rises above a predetermined upper limit and ofopening when the same falls below a predetermined lower limit, andplaced in series in the connecting passage connected to the pilot valveB.

The automatic regulating valve apparatus may further comprise a pilotvalve C operated by a balance of counteracting forces respectivelyproduced by pressure difference across the main valve unit and afixed-pressure applying means, capable of closing when the pressuredifference across the main valve unit rises above a predetermined leveland of opening when the same drops below the predetermined level, afirst float valve capable of closing when liquid level on the downstreamside of the main valve unit rises above a predetermined upper limit andof opening when the same drops below the predetermined upper limit, anda second float valve capable of closing when the liquid level on thedownstream side of the main valve unit rises above a predetermined lowerlimit and of opening when the same drops below the lower limit, whereinthe pilot valve C and the first float valve may be placed in series in aconnecting passage connected to the pilot valve B, and the main valvedriving pressure chamber may be connected through the second float valveto the downstream side of the main valve unit.

The automatic regulating valve apparatus may further comprise a pilotvalve D operated by a balance of counteracting forces respectivelyproduced by a pressure difference across the restrictor and afixed-pressure applying means, capable of opening when the pressuredifference across the restrictor rises above a predetermined level andof closing when the same drops below the predetermined level, a firstfloat valve capable of closing when liquid level on the downstream sideof the main valve unit rises above a predetermined upper limit and ofopening when the same drops below the predetermined upper limit, and asecond float valve capable of closing when the liquid level on thedownstream side of the main valve unit rises above a predetermined lowerlimit and of opening when the same drops below the lower limit, whereinthe pilot valve D and the first float valve may be placed in series in aconnecting passage connected to the pilot valve B, and the main valvedriving pressure chamber may be connected through the second float valveto the downstream side of the main valve unit.

Three valve elements of the pilot valves A, B and D may be disposedcoaxially so as to move together according to the balance of thecounteracting forces produced by the pressure difference across therestrictor and the fixed-pressure applying means.

The present invention provides an automatic regulating valve apparatuscomprising a main valve unit and a pilot valve unit operativelyconnected to the main valve unit to control the main valve unit, whereinthe main valve unit comprises a main valve casing, a main valve elementdisposed in the main valve casing, and a main valve driving memberdisposed in the main valve casing together with the main valve elementand having a pressure receiving area greater than that of the main valveelement, the main valve element is disposed on an upstream side of avalve seat so as to form a restricting passage between the main valveelement and the main valve seat, the main valve driving member isdisposed for sliding movement in a space defined by a cylindrical wallformed in the main valve casing so as to define a main valve drivingpressure chamber together with the cylindrical wall, the pilot valveunit comprises a pilot valve A and a pilot valve B operated by a balanceof counteracting forces respectively produced by a pressure differenceacross the main valve unit and a fixed-pressure applying means, thepilot valve A is capable of opening when the pressure difference acrossthe main valve unit rises above a predetermined level and of closingwhen the same drops below the predetermined level, the pilot valve B iscapable of closing when the pressure difference across the main valveunit rises above the predetermined level and of opening when the samedrops below the predetermined level, the pilot valves A and B arearranged in series and connected between the upstream and the downstreamside of the main valve unit by connecting passages with a chamberbetween the pilot valves A and B connected to the main valve drivingpressure chamber, a first float valve capable of closing when liquidlevel on a downstream side of the main valve unit rises above apredetermined upper limit and of opening when the same drops below thepredetermined upper limit and a second float valve capable of closingwhen the liquid level on the downstream side of the main valve unitrises above a predetermined lower limit and of opening when the samedrops below the lower limit are employed, the first float valve isplaced in series in a connecting passage connected to the pilot valve B,and the main valve driving pressure chamber is connected through thesecond float valve to the downstream side of the main valve unit.

The present invention provides an automatic regulating valve apparatuscomprising a main valve unit and a pilot valve unit operativelyconnected to the main valve unit to control the main valve unit, whereinthe main valve unit comprises a main valve casing, a main valve elementdisposed in the main valve casing, and a main valve driving memberdisposed in the main valve casing together with the main valve elementand having a pressure receiving area greater than that of the main valveelement, the main valve element is disposed on an upstream side of avalve seat so as to form a restricting passage between the main valveelement and the main valve seat, the main valve driving member isdisposed for sliding movement in a space defined by a cylindrical wallformed in the main valve casing so as to define a main valve drivingpressure chamber together with the cylindrical wall, the pilot valveunit comprises a pilot valve A and a pilot valve B which are operativelyconnected to a float which moves vertically according to the variationof liquid level on a downstream side of the main valve unit, the pilotvalve A opens when the float rises and closes when the float falls, thepilot valve B closes when the float rises and opens when the floatfalls, and the pilot valves A and B are arranged in series and connectedbetween the upstream and the downstream side of the main valve unit byconnecting passages with a chamber between the pilot valves A and Bconnected to the main valve driving pressure chamber.

The present invention provides an automatic regulating valve apparatuscomprising a main valve unit and a pilot valve unit operativelyconnected to the main valve unit to control the main valve unit, whereinthe main valve unit comprises a main valve casing, a main valve elementdisposed in the main valve casing, and a main valve driving memberdisposed in the main valve casing together with the main valve elementand having a pressure receiving area greater than that of the main valveelement, the main valve element is disposed on an upstream side of avalve seat so as to form a restricting passage between the main valveelement and the main valve seat, the main valve driving member isdisposed for sliding movement in a space defined by a cylindrical wallformed in the main valve casing so as to define a main valve drivingpressure chamber together with the cylindrical wall, the pilot valveunit comprises a pilot valve A and a pilot valve B which are operated bya balance of counteracting forces respectively produced by pressuredifference across the main valve unit and a fixed-pressure applyingmeans, the pilot valve A opens when the pressure difference across themain valve unit rises above a predetermined level and closes when thesame drops below the predetermined level, the pilot valve B closes whenthe pressure difference across the main valve unit rises above thepredetermined level and opens when the same drops below thepredetermined level, the pilot valve A and the pilot valve B arearranged in series and connected between the upstream and the downstreamside of the main valve unit by connecting passages with a chamberbetween the pilot valves A and B connected to the main valve drivingpressure chamber.

The present invention provides an automatic regulating valve apparatuscomprising a main valve unit and a pilot valve unit operativelyconnected to the main valve unit to control the main valve unit, whereinthe main valve unit comprises a main valve casing, a main valve elementdisposed in the main valve casing, and a main valve driving memberdisposed in the main valve casing together with the main valve elementand having a pressure receiving area greater than that of the main valveelement, the main valve element is disposed on an upstream side of avalve seat so as to form a restricting passage between the main valveelement and the main valve seat, the main valve driving member isdisposed for sliding movement in a space defined by a cylindrical wallformed in the main valve casing so as to define a main valve drivingpressure chamber together with the cylindrical wall, the pilot valveunit comprises a pilot valve A and a pilot valve B which are operated bya balance of counteracting forces respectively produced by pressure onthe upstream side of the main valve unit and a fixed-pressure applyingmeans, the pilot valve A closes when the pressure on the upstream sideof the main valve unit rises above a predetermined level and opens whenthe same drops below the predetermined level, the pilot valve B openswhen the pressure on the upstream side of the main valve unit risesabove the predetermined level and closes when the same drops below thepredetermined level, the pilot valves A and B are arranged in series andconnected between the upstream and the downstream side of the main valveunit by connecting passages with a chamber between the pilot valves Aand B connected to the main valve driving pressure chamber.

According to the present invention, the cylindrical wall of the mainvalve casing may have a cylindrical part and a reduced cylindrical partcoaxial with the cylindrical part, the main valve driving member may beprovided on its peripheral part with a piston part and an expandedpiston part coaxial with the piston part, the expanded piston part maycome into sliding contact with the cylindrical part and the piston partmay come into sliding contact with the reduced cylindrical part when themain valve driving member moves in a predetermined section of a range ofmovement of the main valve driving member to form a damping chamber fordampening the movement of the main valve driving member.

The automatic regulating valve apparatus may be contained in a caseprovided with connecting openings to be connected to external conduits.

In the automatic regulating valve apparatus thus constructed inaccordance with the present invention, the pressure in the main valvedriving pressure chamber is varied properly by the coordinatedoperations of the pilot valves A and B which opens and closes accordingto the variation of the pressure difference across the restrictor, thepressure difference across the main valve unit, the liquid level on thedownstream side of the main valve unit or the pressure on an upstreamside of the main valve unit to adjust the position of the main valveelement relative to the main valve seat for the automatic control of thefluid flowing through the automatic-control valve to achieve excellentautomatic control functions including a constant-flow control function,an emergency shutoff function, a liquid level control function and anupstream pressure control function. The automatic-control valve iscapable of readily achieving perfectly sealed shutoff.

Since both the pilot valves A and B are not provided with any fixedrestricting passage, such as a needle valve, the pilot valves A and Bare not easily clogged with sand or dust. If, by any chance, the pilotvalves A and B should be clogged, the pilot valves A and B open inresponse to pressure change resulting from clogging to exercise aclogging preventing function achieved by a self-cleaning operation.

The pilot valves A and B operate coordinately to combine the pressure onthe upstream side of the main valve unit and the pressure on thedownstream side of the main valve unit in the pilot valve unit, and thecombined pressure is applied to the main valve driving pressure chamberto respond quickly to the variation of the flowing mode of the fluid.Thus, the automatic-control valve is capable of operating quicklywithout entailing chattering and hunting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of an automatic regulating valveapparatus in a first embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claims 1and 2;

FIG. 2 is a longitudinal sectional view of an automatic regulating valveapparatus in a second embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claims 1and 3;

FIG. 3 is a longitudinal sectional view of an automatic regulating valveapparatus in a third embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claims 1and 2;

FIG. 4 is a longitudinal sectional view of an automatic regulating valveapparatus in a fourth embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claims 1and 2;

FIG. 5 is a longitudinal sectional view of an automatic regulating valveapparatus in a fifth embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claims 1and 2;

FIG. 6 is a longitudinal sectional view of an automatic regulating valveapparatus in a sixth embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claims 1and 3;

FIG. 7 is a longitudinal sectional view of an automatic regulating valveapparatus in a seventh embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claim 4;

FIG. 8 is a longitudinal sectional view of an automatic regulating valveapparatus in an eighth embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claim 5;

FIG. 9 is a longitudinal sectional view of an automatic regulating valveapparatus in a ninth embodiment of the present invention most closelyrelating to an automatic regulating valve apparatus stated in claim 6;

FIG. 10 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a tenth embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaim 7;

FIG. 11 is a longitudinal sectional view of an automatic regulatingvalve apparatus in an eleventh embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaims 8 and 9:

FIG. 12 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a twelfth embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaims 8 and 9;

FIG. 13 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a thirteenth embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaim 10;

FIG. 14 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a fourteenth embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaim 10;

FIG. 15 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a fifteenth embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaims 11 and 14;

FIG. 16 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a sixteenth embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaims 11 and 14;

FIG. 17 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a seventeenth embodiment of the present inventionmost closely relating to an automatic regulating valve apparatus statedin claims 11 and 14;

FIG. 18 is a longitudinal sectional view of an automatic regulatingvalve apparatus in an eighteenth embodiment of the present inventionmost closely relating to an automatic regulating valve apparatus statedin claim 12;

FIG. 19 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a nineteenth embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaim 12;

FIG. 20 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a twentieth embodiment of the present invention mostclosely relating to an automatic regulating valve apparatus stated inclaim 13;

FIG. 21 is a longitudinal sectional view of an automatic regulatingvalve apparatus in a twenty-first embodiment of the present inventionmost closely relating to an automatic regulating valve apparatus statedin claim 13;

FIG. 22 is a longitudinal sectional view (partly in a front elevation)of an automatic regulating valve apparatus in a twenty-second embodimentof the present invention most closely relating to an automaticregulating valve apparatus stated in claim 15;

FIG. 23 is a longitudinal sectional view of a prior art direct-actingconstant-flow valve; and

FIG. 24 is a longitudinal sectional view of a prior art pilot-operatedliquid level control valve.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail with reference to theaccompanying drawings.

In the following description, a pilot valve A and a valve elementincluded in the pilot valve A will be referred to as “A valve” and “Avalve element”, respectively, a pilot valve B and a valve elementincluded in the pilot valve B will be referred to as “B valve” and “Bvalve element”, respectively, a pilot valve C and a valve elementincluded in the pilot valve C will be referred to as “C valve” and “Cvalve element”, respectively, a pilot valve D and a valve elementincluded in the pilot valve D will be referred to as “D valve” and “Dvalve element”, respectively, a passage on the upstream side of a mainvalve unit will be referred to as “upstream passage”, pressure in theupstream passage is referred to as “primary pressure”, a passage on thedownstream side of the main valve unit will be referred to as“downstream passage” and pressure in the downstream passage will bereferred to as “secondary pressure” for convenience' sake. Parts capableof the same functions are designated by the same reference charactersthroughout the drawings.

A first embodiment of the present invention will be described withreference to FIG. 1. An automatic regulating valve apparatus in thefirst embodiment is a constant-flow valve apparatus.

Referring to FIG. 1, a main valve unit has a main valve casing 1 havingan inlet passage a (a1 and a2) and an outlet passage c, a main valve top2 and a main valve seat 4. Arranged in the main valve casing 1 are amain valve element 5 disposed on the upstream side of the main valveseat 4, a main valve driving member 6 fitted for sliding movement in aspace defined by a cylindrical wall 3 formed in the main valve casing 1and provided with a sealing member 6 s for making a sealed joint, whichmay be a loose sealed joint capable of preventing only natural leakage,between the main valve driving member 6 and the cylindrical wall 3, anda main valve stem 7. The main valve element 5 and the main valve drivingmember 6 are held in combination on the main valve stem 7. The mainvalve stem 7 is supported for axial movement in a bearing 10. A closedmain valve driving pressure chamber d is defined by the main valvedriving member 6, the cylindrical wall 3 and the main valve top 2. Thepressure in the main valve driving pressure chamber d is controlled tocontrol the main valve element 5 for opening and closing a main valveopening b formed between the main valve element 5 and the main valveseat 4. The pressure receiving area of the main valve driving member 6is somewhat greater than that of the main valve element 5.

A restrictor 11 is disposed in a passage extending through the mainvalve unit. In this embodiment, the restrictor 11 is of a movable typecapable of being operated for flow control by operating a handwheel 12.

Pressure difference across the restrictor 11 varies according to thevariation of flow rate. An A valve opens when the pressure differenceacross the restrictor 11 rises beyond a predetermined level and closeswhen the same drops below the predetermined level. A B valve closes whenthe pressure difference across the restrictor 11 rises beyond thepredetermined level and opens when the same drops below thepredetermined level. The pilot valve A and the pilot valve B arearranged in series and connected between the upstream and the downstreamside of the main valve unit by connecting passages with a chamberbetween the A valve and the B valve connected to the main valve drivingpressure chamber d. Thus, the main valve driving pressure chamber dserves as an operating pressure chamber for driving the main valve unit.

As shown in FIG. 1, the pilot valve unit has a valve casing 21 and avalve top 22. The valve casing 21 has an A valve chamber f for the Avalve, a B valve chamber h for the B valve, an intermediate chamber gformed between the A valve and the B valve, and an ante-restrictorpressure chamber i. An A valve element 24 is fitted in the A valvechamber f, a B valve element 25 is fitted in the B valve chamber h, andthe intermediate chamber g is formed between the A valve chamber f andthe B valve chamber h. The A valve element 24 and the B valve element 25are coaxial lands formed on a spool, and form a cylinder-piston valveopening/closing mechanism so as not to interfere with each other. Thedistance between the A valve element 24 and the B valve element 25 aredetermined so as to create a state where one of the A valve and the Bvalve is open and the other is closed and a state where both the A valveand the B valve are substantially closed. Indicated at 23 is a pressurereceiving plate, at 23 s is a sealing member, at 26 is a spool forcombining the valve elements 24 and 25 with the pressure receiving plate23. A post-restrictor pressure chamber j and a spring chamber k areformed in the valve top 22. A spring 27 (a compression coil spring inthis embodiment), i.e., fixed-pressure applying means, is contained inthe spring chamber k. The spring chamber k may be formed in a sealedchamber to use the same as the post-restrictor pressure chamber j.

Both the valve elements 24 and 25 need not be capable of tight sealingfor valve closing operation and may allow slight leakage. Needless tosay, the valve elements 24 and 25 may be capable of tight sealing.

The ante-restrictor pressure chamber i is connected to the passage a1 onthe upstream side of the restrictor 11 by a connecting passage r1, andthe post-restrictor pressure chamber j is connected to the passage a2 onthe downstream side of the restrictor 11 by a connecting passage r2. TheA valve chamber f is connected to the passage a2 by a connecting passagep to apply a primary pressure, i.e., pressure in the passage a2, to thesame, the intermediate chamber g is connected to the main valve drivingpressure chamber d by a connecting passage m, and the B valve chamber his connected to the outlet passage c by a connecting passage q to applya secondary pressure to the same.

The operation of the present invention will be described with referenceto FIG. 1 showing the first embodiment. In FIG. 1, the arrows indicatesthe flowing direction of a fluid.

When the restrictor 11 is fully open, an opening defined by therestrictor 11 provides only a slight resistance. In this state, theforce of the spring 27 exceeds a force produced by the pressuredifference between the ante-restrictor pressure chamber i and thepost-restrictor pressure chamber j, i.e., the pressure difference acrossthe restrictor 11 and hence the pressure receiving plate 23 is pressedin the direction of extension of the spring 27. Consequently, the Avalve element 24 is at a closing position to close the A valve, the Bvalve element 25 is at an opening position to open the B valve, andhence the secondary pressure prevails in the main valve driving pressurechamber d. Therefore, the main valve element 5 is moved away from themain valve seat 4 by a force corresponding to the difference between therespective pressure receiving areas of the main valve element 5 and themain valve driving member 6, and the fluid flows through the inletpassages a1 and a2→a main valve opening b→the outlet passage c.

Needless to say, the spring 27 is designed so that the same is able toexert forces capable of counterbalancing the pressure differences acrossthe restrictor 11.

When the opening defined by the restrictor 11 is reduced to regulate theflow of the fluid, resistance exerted on the fluid by the openingincreases. Then, in the pilot valve unit, the force corresponding to thepressure difference between the ante-restrictor pressure chamber i andthe post-restrictor pressure chamber j, i.e., the pressure differenceacross the restrictor 11, exceeds the force of the spring 27, and thepressure receiving plate 23 is pressed in a direction to compress thespring 27. Consequently, the A valve element 24 moves to an openingposition to open the A valve, the B valve element 25 moves to a closingposition to close the B valve, and hence the pressure in the main valvedriving pressure chamber d rises toward the primary pressure. Therefore,the main valve element 5 is moved in a closing direction by a forcecorresponding to the difference between pressures acting on the oppositesides thereof, respectively, and, eventually, the main valve opening bis adjusted automatically to a size corresponding to a flow rate set byoperating the restrictor 11.

After the pressure difference across the restrictor 11 has reached apredetermined value, the A valve element and the B valve element aremoved according to the variation of the pressure difference across therestrictor 11 due to the variation of the flow rate of the fluid on theupstream side. Thus the pressure in the main valve driving pressurechamber d is varied properly and the opening defined by the main valveelement 5 and the main valve seat 4 is regulated to maintain the flowrate constant. Both the valve elements 24 and 25 are held stably atclosing positions to close the A valve and the B valve substantiallywhile the pressure difference across the restrictor 11 is stable.

The main valve unit can be set for a desired flow rate by operating therestrictor 11 by means of the handwheel 12 or the like. The fineadjustment of the flow rate can be achieved simply by adjusting theresilience of the spring 27 by means of an adjusting screw 28.

When the restrictor 11 is fully closed, the pressure receiving plate 23of the pilot valve unit is pressed in a direction to compress the spring27, the A valve element 24 is moved to the opening position to open theA valve and the B valve element 25 is moved to the closing position toclose the B valve. Consequently, the main valve element 5 is pressedagainst the main valve seat 4. A sealing member, not shown, for therestrictor 11 must be capable of easily forming a tight sealed joint bya conventional technique. The fluid does not leak downstream even if themain valve driving member 6, the A valve element 24 and the B valveelement 25 form loose sealed joints.

Since both the A valve and the B valve are not provided with any fixedflow control passage, such as a needle valve, the A valve and the Bvalve are rarely clogged with sand or dust. If, by any chance, the Avalve and the B valve should be clogged, the valve elements 24 and 25are moved automatically to the opening positions to open the A valve andthe B valve in response to pressure change for a self-cleaningoperation. Suppose, for example, that the A valve having the A valveelement 24 is clogged. Then, the fluid of the primary pressure is unableto flow through the connecting passage p into the main valve drivingpressure chamber d, the pressure in the main valve driving pressurechamber d decreases, the main valve element 5 is moved in an openingdirection, and the flow rate of the fluid increases. Consequently, thepressure difference across the restrictor 11 increases, the forcecorresponding to the pressure difference exceeds the force of the spring27, and the A valve element 24 is moved in an opening direction, so thatmatters clogging the A valve are removed automatically. Since the Avalve and the B valve are capable of such a self-cleaning operation, thepilot valve unit need not be provided with a strainer of a fine mesh andwork for the maintenance and management of the pilot valve unit isfacilitated.

Since the A valve element 24 and the B valve element 25 are arranged onthe spool 26 so as to move together relative to the fixed-pressureapplying means (the spring 27), and the pilot valve unit has a simple,reasonable configuration capable of combining the primary and thesecondary pressure therein and of quickly responding to the variation ofthe flow of the fluid by applying the combined pressure to the mainvalve driving pressure chamber d. The distance between the A valveelement 24 and the B valve element 25 are determined so that the A valveelement and the B valve element can be set in a state where one of the Avalve and the B valve is open and the other is closed and in a statewhere both the A valve and the B valve are substantially closed. Whenthe flow is stable, both the valve elements become stable substantiallyat the closing position and hence the chattering or hunting operation ofthe valve elements rarely occurs.

A second embodiment through a twenty-second embodiment will be describedwith reference to FIGS. 2 to 22.

As shown in FIG. 2, a constant-flow valve apparatus in a secondembodiment according to the present invention has a pilot valve unitdifferent from that of the constant-flow valve apparatus in the firstembodiment. The constant-flow valve apparatus shown in FIG. 2 has apilot valve unit provided with an A valve element 24 and a B valveelement 25 disposed in an intermediate chamber g and a spring 27 whichexerts a force in a direction opposite to the direction in which thespring 27 of the first embodiment exerts its force for the samefunction, and a main valve unit provided with a replaceable orificeplate 11 instead of the restrictor 11 employed in the first embodiment.The constant-flow valve apparatus can be set for a desired flow rate byadjusting the resilience of the spring 27 by means of an adjusting screw28.

A valve 29 placed in a connecting passage q connected to a B valve isused to close the main valve unit forcibly regardless of the operationof the pilot valve unit. Normally, the valve 29 is open. When it isdesired to close the main valve unit, the valve 29 is closed.Consequently, the pressure in a main valve driving pressure chamber drises toward the primary pressure, a main valve element 5 is moved in aclosing direction, and a sealing member 5 s attached to the main valveelement 5 and a sealing member, not shown, included in the valve 29 formsealed joints.

Although the constant-flow valve apparatus in the second embodiment issomewhat different as mentioned above from the constant-flow valveapparatus in the first embodiment because the second embodiment is amodification of the first embodiment, the constant-flow valve apparatusin the second embodiment is similar in other respects, functions andeffects to that in the first embodiment and hence further descriptionthereof will be omitted.

As shown in FIG. 3, a constant-flow valve apparatus in a thirdembodiment according to the present invention has a pilot valve unitdifferent from that of the constant-flow valve apparatus in the firstembodiment. The constant-flow valve apparatus shown in FIG. 3 has apilot valve unit provided with an A valve element 24 and a B valveelement 25 disposed in an intermediate chamber g, and a main valve unitprovided with a main valve driving member 6 disposed on the downstreamside of a main valve seat 4. Although the directions of movement of themain valve driving member 6 for functions are opposite to those of themain valve driving member 6 employed in the first embodiment for thesame functions, an A valve and a B valve are placed in the order reverseto that in which the A valve and the B valve are arranged in the firstembodiment, and the connection of connecting passages connecting an Avalve and a B valve to an inlet passage a and an outlet passage c isreverse to that of the corresponding connecting passages to the inletpassage a and the outlet passage c in the first embodiment because thethird embodiment is a modification of the first embodiment, the thirdembodiment is similar in other respects, functions and effects to thatin the first embodiment and hence further description thereof will beomitted.

Although it is desirable to provide the main valve unit with a mainvalve spring 9 as shown in FIG. 3 to ensure the stable movement of themain valve element 5 at the start of passing a fluid through the mainvalve unit, the main valve spring 9 does not exercise any particulareffect after the fluid has started flowing through the main valve unitand hence the main valve spring 9 may be omitted.

As shown in FIG. 4, a constant-flow valve apparatus in a fourthembodiment according to the present invention has a pilot valve unitdifferent from that of the constant-flow valve apparatus in the firstembodiment. The constant-flow valve apparatus shown in FIG. 4 has apilot valve unit provided with an A valve element 24 and a B valveelement 25 disposed in an intermediate chamber g and a spring 27 whichexerts a force in a direction opposite to the direction in which thespring 27 of the first embodiment exerts its force for the samefunction, and a main valve unit provided with a restrictor 11 disposedon the downstream side thereof. Although the constant-flow valveapparatus in the fourth embodiment is somewhat different as mentionedabove from the constant-flow valve apparatus in the first embodimentbecause the fourth embodiment is a modification of the first embodiment,the constant-flow valve apparatus in the fourth embodiment is similar inother respects, functions and effects to that in the first embodimentand hence further description thereof will be omitted.

As shown in FIG. 5, a constant-flow valve apparatus in a fifthembodiment according to the present invention is provided with a mainvalve element serving as both a main valve element 5 and a main valvedriving member 6 and disposed so as to move in directions along thedirection of flow of a fluid through inlet passages a1 and a2 toward anoutlet passage c. The constant-flow valve apparatus in the fifthembodiment is similar in other respects, functions and effects to thatin the first embodiment and hence further description thereof will beomitted.

As shown in FIG. 6, a constant-flow valve apparatus in a sixthembodiment according to the present invention is similar in constructionas that in the second embodiment. As shown in FIG. 6, the constant-flowvalve apparatus in the sixth embodiment is provided with a main valveelement serving as both a main valve element 5 and a main valve drivingmember 6 and disposed so as to move in directions along the direction offlow of a fluid through inlet passages al and a2 toward an outletpassage c, and an orifice plate 11 provided with grooves in the frontand the back surface thereof to prevent the influence of turbulent flowson the pressure difference across the orifice plate 11. Theconstant-flow valve apparatus in the sixth embodiment is similar inother respects, functions and effects to that in the second embodimentand hence further description thereof will be omitted.

As shown in FIG. 7, a constant-flow valve apparatus in a seventhembodiment according to the present invention is formed by placing avalve 29 which closes upon the detection of an abnormal condition in theenvironment by an abnormal condition detector 29 a in the connectingpassage q connected to the B valve of the first embodiment. Theconstant-flow valve apparatus in the seventh embodiment is similar inconstruction to the constant-flow valve apparatus in the firstembodiment and has an emergency shutoff function to shutoff theassociated pipeline automatically in an emergency, such as theoccurrence of a fire or an earthquake or abnormal pressure rise or dropin the associated pipeline in addition to the functions of theconstant-flow valve apparatus in the first embodiment.

When the connecting passage q is closed by the valve 29, the pressure inthe main valve driving pressure chamber d rises to seat the main valveelement 5 on the main valve seat 4. The valve 29 and the abnormalcondition detector 29 a may be combined by a well-known method; thevalve 29 may be driven by an electric signal provided by a detector 29 a(sensor) if the valve 29 is a motor-driven or solenoid-driven valve ormay mechanically be combined with the detector 29 a.

The constant-flow valve apparatus in the seventh embodiment is similarin other respects, functions and effects to that in the first embodimentand hence further description thereof will be omitted.

Needless to say, the second to the sixth embodiment, as well as thefirst embodiment, may additionally be provided with the valve 29 and theabnormal condition detector 29 a.

As shown in FIG. 8, a valve apparatus in an eighth embodiment of thepresent invention is formed by placing a valve 30 which closes when theliquid level on the downstream side of the main valve rises above apredetermined liquid level and opens when the liquid level falls belowthe predetermined liquid level in the connecting passage q connected tothe B valve of the first embodiment. The constant-flow valve apparatusin the eighth embodiment has a liquid level control function in additionto the functions of the constant-flow valve in the first embodiment.

As shown in FIG. 8, a valve 30 is, for example, a generally known floatvalve 30 disposed near the surface of the liquid on the downstream sideof a main valve. The float valve 30 opens when the liquid level is lowerthan a predetermined liquid level to enable the fluid to flow through aconnecting passage q and closes upon the rise of the liquid level to thepredetermined liquid level.

Since the valve apparatus functions as a constant-flow valve apparatuswhile the liquid level is lower than the predetermined level, the liquidis delivered very moderately and the liquid is not supplied at anexcessively high flow rate even if the primary pressure is high. Whenthe liquid level reaches the predetermined liquid level, the float valve30 closes, the pressure in a main valve driving pressure chamber d risesto seat a main valve element 5 on a main valve seat 4, and a sealingmember 5 s attached to the main valve element 5, and a sealing member,not shown, included in the float valve 30 form sealed joints.

The constant-flow valve apparatus in the eighth embodiment is similar inother respects, functions and effects to that in the first embodimentand hence further description thereof will be omitted.

Needless to say, the second to the seventh embodiment, as well as thefirst embodiment, may additionally be provided with the float valve 30.

A valve apparatus in a ninth embodiment of the present invention issimilar in construction to the valve apparatus in the eighth embodiment.As shown in FIG. 9, the valve apparatus in the ninth embodiment isprovided with a float valve 30 similar to the float valve 30 employed inthe eighth embodiment. The float valve 30 shown in FIG. 9 closes whenthe liquid level on the downstream side of a main valve unit rises abovean upper limit liquid level (HWL) and opens when the liquid level fallsbelow a lower limit liquid level (LWL) to control the liquid levelbetween the upper limit liquid level and the lower limit liquid level.

A float 30 b of the float valve 30 placed in series in a connectingpassage q is supported on a float shaft 30 a for movement betweenstoppers disposed at a position near the upper end of the float shaft 30a and a position near the lower end of the float shaft 30 a. It isdesirable to brake the float shaft 30 a by applying a frictionalresistance to the float shaft 30 a or to apply a fixed force to thevalve element of the float valve 30 to settle the valve element in anopen state or a closed state to prevent the movement of the float shaft30 a by a frictional dragging action of the float 30 b sliding along thefloat shaft 30 a according to the variation of the liquid level betweenthe upper and the lower limit liquid level, and the resultant faultyoperation of the float valve apparatus 30.

The float 30 b comes into contact with the stopper attached to the floatshaft 30 a at a position near the lower end of the float shaft 30 a anddepresses the float shaft 30 a when the liquid level falls to thepredetermined lower limit liquid level. Consequently, the float valve 30is opened, the pressure in a main valve driving pressure chamber ddrops, a main valve element 5 is moved away from a main valve seat 4,and the liquid is supplied downstream through the main valve unit. Inthis state, the valve apparatus serves as a constant-flow valveapparatus.

The float 30 b comes into contact with the stopper attached to the floatshaft 30 a at a position near the upper end of the float shaft 30 a andpushes up the float shaft 30 a when the liquid level rises to thepredetermined upper limit liquid level. Consequently, the float valve 30is closed, the pressure in the main valve driving pressure chamber drises, the main valve element 5 is seated on the main valve seat 4. Inthis state, a sealing member 5 s attached to the main valve element 5and a sealing member, not shown, included in the float valve 30 formsealed joints.

The valve apparatus in the ninth embodiment is similar in otherrespects, functions and effects to that in the eighth embodiment andhence the further description thereof will be omitted.

A valve apparatus in a tenth embodiment of the present invention issimilar in construction to the valve apparatus in the ninth embodiment.As shown in FIG. 10, the valve apparatus in the tenth embodiment isprovided with two float valves 36 and 37 assigned to the detection ofthe liquid level to the predetermined upper limit liquid level and tothe predetermined lower limit liquid level, respectively. The valveapparatus of this configuration is suitable when the difference betweenthe upper limit and the lower limit liquid level is great.

The valve apparatus in the tenth embodiment is provided, instead of thefloat valve 30 employed in the ninth embodiment, with a C valve whichcloses when the pressure difference across a main valve unit rises abovea predetermined value and opens when the same falls below thepredetermined value, the first float valve 36 which closes when theliquid level on the downstream side of the main valve unit rises abovethe predetermined upper liquid level and opens when the same falls belowthe upper limit liquid level, and the second float valve 37 which closeswhen the liquid level on the downstream side of the main valve unitrises above the lower limit liquid level and opens when the same fallsbelow the predetermined lower limit liquid level. The C valve and thefirst float valve 36 are placed in series in a connecting passage q1connected to a B valve. A main valve driving pressure chamber d isconnected to the second float valve 37 by a connecting passage q2.

A C valve element 31 included in the C valve is formed integrally with aspool 34 separate from a spool 26 included in A and B valves, and apressure receiving plate 33 included in the C valve is fixedly mountedon the spool 34. A primary pressure chamber v and a secondary pressurechamber w are formed on the opposite sides of the pressure receivingplate 33, respectively. The primary pressure chamber v is connected tothe inlet passage a1 by a connecting passage r1, and the secondarypressure chamber w is connected to the outlet passage c by a connectingpassage r3.

Both the first float valve 36 and the second float valve 37 are open andhence the pressure in the main valve driving pressure chamber d is equalto the secondary pressure while the liquid level is below thepredetermined lower limit liquid level. Therefore, a main valve element5 is at its fully open position and the liquid flows at a maximum flowrate toward the downstream side of the main valve unit. In this state,the pressure difference between the primary pressure chamber v and thesecondary pressure chamber w, i.e., the pressure difference across themain valve unit, is small, the force of a spring 35 exceeds a forcecorresponding to the pressure difference between the primary pressurechamber v and the secondary pressure chamber w, and hence the C valve isopen.

The second float valve 37 closes first when the liquid level rises asthe liquid is supplied. In this state, the C valve element 31 is stillat an open position and the first float valve 36 is open. Therefore, thepressure in the main valve driving pressure chamber d is controlled bythe A valve and the B valve, and the valve apparatus serves as aconstant-flow valve apparatus to enable the liquid to flow through themain valve unit toward the downstream side at a constant flow rate.Since the C valve element 31 is at its open position and does not affectthe flow of the liquid through the connecting passage q1 caused by theoperation of the A valve and the B valve, the C valve element 31 doesnot interfere with a constant-flow control function.

When the liquid level reaches the predetermined upper limit liquidlevel, the first float valve 36 closes, the pressure in the main valvedriving pressure chamber d rises toward the primary pressure to seat themain valve element 5 on the valve seat 4. In this state, the sealingmember 5 s attached to the main valve element 5, and sealing members,not shown, included in the float valves 36 and 37 form sealed joints.The pressure difference between the primary pressure chamber v and thesecondary pressure chamber w increases, and a force corresponding to thepressure difference between the primary pressure chamber v and thesecondary pressure chamber w exceeds the force of the spring 35 and theC valve element 31 is pressed against a C valve seat 32 to close the Cvalve.

The liquid level on the downstream side of the main valve unit falls asthe liquid is used. Then, the first float valve 36 opens, while the Cvalve is still closed and the second float valve 37 is closed.Therefore, the pressure in the main valve driving pressure chamber d isequal to the primary pressure and the main valve unit remains closed.

When the liquid level falls further to the predetermined lower limitliquid level, the second float valve 37 opens, the pressure in the mainvalve driving pressure chamber d decreases toward the secondarypressure, the main valve element 5 is moved away from the main valveseat 4, and the liquid is supplied through the main valve unit at themaximum flow rate. In this state, the pressure difference between theprimary pressure chamber v and the secondary pressure chamber wdecreases, the force of the spring 35 exceeds a force corresponding tothe pressure difference between the primary pressure chamber y and thesecondary pressure chamber w, and the C valve element 31 is separatedfrom the C valve seat 32.

Thus the liquid level is controlled so as to vary in the range betweenthe predetermined upper limit liquid level and the predetermined lowerlimit liquid level.

The main valve unit is provided with a replaceable fixed orifice plate11, and a desired flow rate can be set by adjusting the resilience ofthe spring 27.

The valve apparatus in the tenth embodiment is similar in otherrespects, functions and effects to that in the ninth embodiment andhence further description thereof will be omitted.

A valve apparatus in an eleventh embodiment of the present inventionshown in FIG. 11 is similar in construction to that in the tenthembodiment, except that the valve apparatus in the eleventh embodimentemploys, instead of the C valve, a D valve which is more compact thanthe C valve.

The D valve opens when the pressure difference across an orifice plate11 is larger than a predetermined value and closes when the same issmaller than the predetermined value. The D valve and a first floatvalve 36 are placed in series in a connecting passage q1 connected to aB valve, and a main valve driving pressure chamber d is connected to asecond float valve 37 by a connecting passage q2. An A valve element 24,a B valve element 25 and a D valve element 41 are formed integrally witha pilot spool. The three valve elements 24, 25 and 41 are moved togetherby the balance of counteracting forces exerted by the pressuredifference across the orifice plate 11 and a spring 27 so that the samemay not obstruct each other.

The operation of the valve apparatus in the eleventh embodiment isdifferent from that of the valve apparatus in the tenth embodiment. TheC valve element included in the C valve employed in the tenth embodimentis moved to its closed position by a force corresponding to the pressuredifference across the main valve unit which increases when the mainvalve unit is closed. A D valve element included in the D valve employedin the eleventh embodiment is moved to its closed position by the effectof the reduction of the pressure difference across the orifice plate 11to naught when the main valve unit is closed.

When the main valve unit is open for supply of liquid, a forcecorresponding to the pressure difference between an ante-orificepressure chamber i and a post-orifice pressure chamber j, i.e., thepressure difference across the orifice plate 11, counteracts the forceof a spring 27, an A valve element 24 and a B valve element 25 are movedby the balance of those forces, and the D valve element 41 is alwaysseparated from the D valve seat 42 to open the D valve. When the mainvalve unit is closed, the pressure difference across the orifice plate11 drops to zero, and the D valve element 41 is pressed against the Dvalve seat 42 by the force of the spring 27 to close the D valve.

Thus, the valve apparatus, similarly to the valve apparatus in the tenthembodiment, is capable of controlling the liquid level between an upperlimit liquid level and a lower limit liquid level. The valve apparatusin the eleventh embodiment is similar in other respects, functions andeffects to that in the tenth embodiment and hence further descriptionthereof will be omitted.

As shown in FIG. 12, a valve apparatus in a twelfth embodiment accordingto the present invention is similar in construction to that in theeleventh embodiment, except that the former has a pilot valve unitdifferent from that of the valve apparatus in the eleventh embodiment.As shown in FIG. 12, an A valve element 24 and a B valve element 25 aredisposed in an intermediate chamber g, a spring 27 exerts a force in adirection opposite to the direction in which the spring 27 of theeleventh embodiment exerts its force for the same function, and a Dvalve element 41 moves in directions opposite to those in which the Dvalve element 41 in the eleventh embodiment moves for the samefunctions. Although the arrangement of connecting passages in thetwelfth embodiment is somewhat different from that of the correspondingconnecting passages in the eleventh embodiment because the valveapparatus in the twelfth embodiment is a modification of the valveapparatus in the eleventh embodiment, the valve apparatus in the twelfthembodiment is similar in other respects, functions and effects to thatin the eleventh embodiment and hence further description thereof will beomitted.

A valve apparatus in a thirteenth embodiment according to the presentinvention shown in FIG. 13 is formed by removing the constant-flowcontrol functions from the valve apparatus in the eleventh embodimentand is designed specially only for a liquid level control function.

As shown in FIG. 13, the valve apparatus is not provided any memberscorresponding to the orifice plate 11 and the D valve of the valveapparatus in the eleventh embodiment, and a primary pressure chamber iand a secondary pressure chamber j are formed on the opposite sides of apressure receiving plate 23 and connected to an inlet passage a and anoutlet passage c, respectively. An A valve and a B valve are operatedfor opening and closing according to the variation of the pressuredifference across a main valve unit to control the liquid level betweena predetermined upper limit liquid level and a predetermined lower limitliquid level.

While the liquid level is lower than the predetermined lower limitliquid level, a first float valve 36 and a second float valve 37 areopen, the pressure in a main valve driving pressure chamber d is equalto the secondary pressure, and hence a main valve element 5 is at itsopen position to allow the liquid to flow downstream through the mainvalve unit. In this state, in a pilot valve unit, the pressuredifference between the primary pressure chamber i and the secondarypressure chamber j, i.e., pressure difference across the main valveunit, is small, the force of a spring 27 exceeds a force correspondingto the pressure difference, and hence an A valve element 24 is at itsclosed position and a B valve element 25 is at its open position.

When the liquid is supplied continuously and the liquid level rises, thesecond float valve 37 is closed, whereas the B valve element 25 stillremains at its open position and the first float valve 36 still remainsopen, the pressure in the main valve driving pressure chamber d is keptat the secondary pressure and hence the fluid continues flowing throughthe main valve unit.

Upon the rise of the liquid level to the predetermined upper limitliquid level, the first float valve 36 is closed, the pressure in themain valve driving pressure chamber d rises toward the primary pressureto move the main valve element 5 to its closed position, and a sealingmember 5 s attached to the main valve element 5, and sealing members,not shown, included in the float valves 36 and 37 form sealed joints. Inthis state, in the pilot valve unit, the pressure difference between theprimary pressure chamber i and the secondary pressure chamber jincreases and a force corresponding to the pressure difference betweenthe primary pressure chamber i and the secondary pressure chamber jexceeds the force of the spring 27 and, consequently, the A valveelement 24 is moved to its open position and the B valve element 25 ismoved to its closed position.

The liquid level falls as the liquid on the downstream side of the mainvalve unit is used. Then, the first float valve 36 opens first, whilethe B valve element 25 remains at its closed position and the secondfloat valve 37 is closed. Consequently, the pressure in the main valvedriving pressure chamber d remains equal to the primary pressure and themain valve unit remains closed.

The liquid level falls further, and the second float valve 37 opens uponthe fall of the liquid level to the predetermined lower limit liquidlevel. Consequently, the pressure in the main valve driving pressurechamber d decreases toward the secondary pressure, the main valveelement 5 is moved to its open position to resume supplying the liquidthrough the main valve unit. Since the pressure difference between theprimary pressure chamber i and the secondary pressure chamber j is smallin this state, the force of the spring 27 exceeds a force correspondingto the pressure difference, the A valve element 24 is moved to itsclosed position and the B valve element 25 is moved to its openposition.

The valve apparatus does not have any constant-flow control function andis capable of only controlling the liquid level between thepredetermined upper and the predetermined lower limit liquid level. Thevalve apparatus in the thirteenth embodiment is similar in otherrespects, functions and effects to that in the eleventh embodiment andhence further description thereof will be omitted.

A valve apparatus in a fourteenth embodiment of the present inventionshown in FIG. 14 is similar to the valve apparatus in the thirteenthembodiment and is provided with a pilot valve unit different from thatof the valve apparatus in the thirteenth embodiment. As shown in FIG.14, an A valve element 24 and a B valve element 25 are placed in anintermediate chamber g, and a spring 27 exerts a force in a directionopposite to the direction in which the spring 27 of the thirteenthembodiment exerts its force for the same function. Although thearrangement of connecting passages in the fourteenth embodiment issomewhat different from that of the corresponding connecting passages inthe thirteenth embodiment because the valve apparatus in the fourteenthembodiment is a modification of the valve apparatus in the thirteenthembodiment, the valve apparatus in the fourteenth embodiment is similarin other respects, functions and effects to that in the thirteenthembodiment and hence further description thereof will be omitted.

In the fourteenth embodiment, a second float valve 37 need notnecessarily be disposed near a lower limit liquid level; the secondfloat valve 37 may be disposed at an optional position and is able toachieve the remote detection of the liquid level by using connectingmembers, such as rods.

A valve apparatus in a fifteenth embodiment according to the presentinvention shown in FIG. 15 employs the pilot valve unit of thethirteenth embodiment and the float valve structure of the ninthembodiment in combination to achieve the control of the liquid levelbetween an upper limit liquid level and a lower limit liquid level by asimple arrangement.

As shown in FIG. 15, An A valve which opens when a float 30 b rises andcloses when the float 30 b falls, and a B valve which closes when thefloat 30 b rises and opens when the float 30 b falls are arranged inseries and connected between the upstream and the downstream side of amain valve unit by connecting passages with a chamber between the Avalve and the B valve connected to the main valve driving pressurechamber d.

The float 30 b is supported for movement along a float shaft 30 aconnected to a spool 26 included in the pilot valve unit betweenstoppers attached to the float shaft 30 a at positions near the upperend and near the lower end of the float shaft 30 a. A braking device 51exerts a fixed resistance against the movement of the float shaft 30 ato prevent the movement of the float shaft 30 a by a frictional draggingaction of the float 30 b sliding along the float shaft 30 a according tothe variation of the liquid level between the upper and the lower limitliquid level, and the resultant faulty operation of the pilot valveunit.

When the liquid level falls to the predetermined lower limit liquidlevel, the float 30 b comes into contact with the stopper attached tothe float shaft 30 a at the position near the lower end of the floatshaft 30 a and depresses the stopper. Then, an A valve element 24included in the A valve is moved to its closed position, and a B valveelement 25 included in the B valve is moved to its open position.Consequently, the pressure in a main valve driving pressure chamber ddecreases toward the secondary pressure, and a main valve element 5 ismoved to its open position to start supplying the liquid through themain valve unit.

When the liquid level rises to the predetermined upper limit liquidlevel, the float 30 b comes into contact with the stopper attached tothe float shaft 30 a at the position near the upper end of the floatshaft 30 a and pushes up the stopper. Then, the A valve element 24 ismoved to its open position, and the B valve element 25 is moved to itsclosed position. Consequently, the pressure in a main valve drivingpressure chamber d increases toward the primary pressure, and the mainvalve element 5 is moved to its closed position. In this state, asealing member 5 s attached to the main valve element 5 and a sealingmember attached to the B valve element 25 form sealed joints.

Thus, the valve apparatus does not have any constant-flow controlfunction and is capable of only controlling the liquid level between thepredetermined upper and the predetermined lower limit liquid level.

In the valve apparatus shown in FIG. 15, the float shaft 30 a isconnected to the spool 26 in a coaxial arrangement. The float shaft 30 aand the spool 26 may be connected by a mechanism for changing directionsof motions or a linkage capable of multiplying force. The float 30 bneed not necessarily be placed below the pilot valve unit. The liquidlevel can be controlled with respect to a single reference liquid levelif the float 30 b is fixed to the float shaft 30 a.

The valve apparatus shown in FIG. 15 is provided with a dampingmechanism 8 (damper) including a main valve driving member 6 to make themain valve unit operate slowly for opening and closing operations.

The damping mechanism 8 comprises a cylindrical wall 3 disposed in amain valve casing 1 and having a cylindrical part 3 a and a reducedcylindrical part 3 b coaxial with the piston part 3 a, and the mainvalve driving member 6 having a piston part 6 a and an expanded pistonpart 6 b coaxial with the piston part 6 a. When the main valve drivingmember 6 is in a predetermined section (a section in which a main valveelement 5 is close to a main valve seat 4) in the range of movement ofthe main valve driving member 6, the expanded piston part 6 b is insliding contact with the cylindrical part 3 a, and the piston part 6 ais in sliding contact with the reduced cylindrical part 3 b to form adamping chamber 8 for dampening the motion of the main valve drivingmember 6. Timing of starting a dampening operation and damping force canbe determined by properly designing the shape of the space formedbetween the cylindrical wall 3 and the main valve driving member 6 or byforming a small hole connecting the damping chamber 8 to an externalspace and capable of restricting the flow of the liquid.

The valve apparatus in the fifteenth embodiment is similar in otherrespects, functions and effects to that in the thirteenth embodiment andhence further description thereof will be omitted.

A valve apparatus in a sixteenth embodiment of the present inventionshown in FIG. 16 is similar to the valve apparatus in the fifteenthembodiment and is provided with a pilot valve unit different from thatof the valve apparatus in the fifteenth embodiment. As shown in FIG. 16,an A valve element 24 and a B valve element 25 are placed in anintermediate chamber g, two floats 30 b and 30 c are fixed to a floatshaft 30 a at a predetermined upper position and a predetermined lowerposition, respectively, instead of the float 30 b employed in thefifteenth embodiment and mounted on the float shaft 30 a for movementbetween the stoppers.

When the liquid level falls to a predetermined lower limit liquid level,the sum of the respective weights of the two floats 30 b and 30 cexceeds a buoyancy exerted on the float 30 c and, consequently, thefloat shaft 30 a moves downward. When the liquid level rises to apredetermined upper limit liquid level, the sum of buoyancies exerted onthe two floats 30 b and 30 c exceeds the sum of the respective weightsof the two floats 30 b and 30 c and, consequently, the float shaft 30 amoves upward. While the liquid level is in a range between the upper andthe lower limit liquid level, a braking device 51 exerting resistanceagainst the movement of the float shaft 30 a keeps the float shaft 30 astationary. Thus, the functions of the floats 30 b and 30 c are the sameas those of the float 30 b of the fifteenth embodiment.

The valve apparatus in the sixteenth embodiment is similar in otherrespects, functions and effects to that in the fifteenth embodiment andhence further description thereof will be omitted.

A valve apparatus in a seventeenth embodiment of the present inventionshown in FIG. 17 is a compact discharge valve formed by uniting togetherthe pilot valve unit and the main valve unit of the valve apparatus inthe fifteenth embodiment with the float 30 b disposed above the pilotvalve unit. The valve apparatus has a main valve casing 1 having an openoutlet end through which the liquid is discharged, and an inlet endjoined to a conduit 53. The valve apparatus in the seventeenthembodiment is similar in other respects, functions and effects to thatin the fifteenth embodiment and hence further description thereof willbe omitted.

A valve apparatus in an eighteenth embodiment of the present inventionshown in FIG. 18 is an emergency shutoff valve formed by removing thefloat valves and the associated parts from the valve apparatus in thethirteenth embodiment.

An A valve which opens when the pressure difference across a main valveunit rises above a predetermined level and closes when the same fallsbelow the predetermined level, and a B valve which closes when thepressure difference across the main valve unit rises above thepredetermined level and opens when the same falls below thepredetermined level are arranged in series and connected between theupstream and the downstream side of the main valve unit by connectingpassages with a chamber between the A valve and the B valve connected tothe main valve driving pressure chamber d. A primary pressure chamber iand a secondary pressure chamber j formed on the opposite sides of apilot pressure receiving plate 23 are connected to an inlet passage aand an outlet passage c, respectively. The A valve and the B valve opensand closes according to the variation of the pressure difference acrossthe main valve unit. If pressure drops abnormally or flow rate increasesabnormally due to the occurrence of an abnormal condition, such as thebreakage of the conduit on the downstream side of the main valve unit,an emergency conduit shutoff operation is executed.

A valve 52 interposed between connecting passages m and q is used as atrigger for opening the main valve unit to resume the supply of theliquid after the arrangement on the downstream side of the main valveunit has been restored to its normal condition after the emergencyconduit shutoff operation. After the supply of the liquid has beenresumed, the valve 52 is kept closed. The valve 52 may manually beoperated, may be a solenoid valve or a motor-driven valve, or may beoperated in a remote control mode by using an actuator.

The pressure in the main valve driving pressure chamber d becomes equalto the secondary pressure when the valve 52 is opened and, consequently,the main valve element 5 is moved away from the valve seat 4 and theliquid starts flowing through the main valve unit. Then, the valve 52 isclosed. The pressure difference between the primary pressure chamber iand the secondary pressure chamber j, i.e., the pressure differenceacross the main valve unit, is small and the force of the spring 27exceeds a force corresponding to the pressure difference while theliquid is being supplied, the A valve element 24 is at its closedposition and the B valve element 25 is at its open position in the pilotvalve unit.

If the actual flow rate increases beyond a predetermined value due tothe breakage of the downstream conduit caused by a disaster or theexcessive consumption of the liquid, resistance exerted on the flow ofthe liquid by a main valve opening b increases and the pressuredifference between the primary pressure chamber i and the secondarypressure chamber j increase. Consequently, a force corresponding to thepressure difference exceeds the force of the spring 27, the A valveelement 24 is moved to its open position, the B valve element 25 ismoved to its closed position, the pressure in the main valve drivingpressure chamber d rises toward the primary pressure, the main valveelement 5 is brought into contact with the main valve seat 4, and asealing member 5 s attached to the main valve element 5 and a sealingmember attached to the B valve element 25 form sealed joints.

When it is desired to resume the supply of the liquid after restoringthe arrangement on the downstream side of the main valve unit to itsnormal condition, the valve 52 is opened to resume the supply of theliquid by the foregoing process, and the valve 52 is closed after thesupply of the liquid has been resumed. Thus, the valve apparatus servesas an emergency shutoff valve apparatus.

The valve 52 may be interposed between the inlet passage a and theoutlet passage c instead of between the connecting passages m and q.However, if the valve 52 is interposed between the inlet passage a andthe outlet passage c, the valve 52 must be of a bore size greater thanthat of the valve 52 interposed between the connecting passages m and q.The main valve unit can be forcibly closed by closing the connectingpassage q. Therefore, if the main valve unit needs to be closedforcibly, a valve may be placed in the connecting passage q at aposition near the outlet passage c and the valve may be closed whennecessary.

The valve apparatus in the eighteenth embodiment is similar in otherrespects, functions and effects to that in the thirteenth embodiment andhence further description thereof will be omitted.

A valve apparatus in a nineteenth embodiment of the present inventionshown in FIG. 19 is similar to the valve apparatus in the eighteenthembodiment and is provided with a pilot valve unit different from thatof the valve apparatus in the eighteenth embodiment. As shown in FIG.19, an A valve element 24 and a B valve element 25 are placed in anintermediate chamber g, and a spring 27 exerts a force in a directionopposite to the direction in which the spring 27 of the eighteenthembodiment exerts its force for the same function. Although thearrangement of connecting passages in the nineteenth embodiment issomewhat different from that of the corresponding connecting passages inthe eighteenth embodiment because the valve apparatus in the nineteenthembodiment is a modification of the valve apparatus in the eighteenthembodiment, the valve apparatus in the nineteenth embodiment is similarin other respects, functions and effects to that in the eighteenthembodiment and hence further description thereof will be omitted.

A valve apparatus in a twentieth embodiment of the present inventionshown in FIG. 20 is a safety valve apparatus.

An A valve which closes when the pressure on the upstream side of a mainvalve unit (primary pressure) rises above a predetermined level andopens when the same drops below the predetermined level, and a B valvewhich opens when the pressure on the upstream side of the main valveunit (primary pressure) rises above the predetermined level and closeswhen the same drops below the predetermined level are arranged in seriesand connected between the upstream and the downstream side of the mainvalve unit by connecting passages with a chamber between the A valve andthe B valve connected to a main valve driving pressure chamber d. Aprimary pressure chamber i and a spring chamber k are formed on theopposite sides of a pilot pressure receiving plate 23, the primarypressure chamber i is connected to an inlet passage a, and the springchamber k is opened to the atmosphere. The A valve and the B valve areopened and closed according to the variation of the primary pressure. Ifthe primary pressure rises abnormally, the valve apparatus is fullyopened to suppress pressure rise.

The valve apparatus is connected to a branch pipe branched from aconduit 53 for conducting a flow of a liquid. A force exerted by aspring 27 exceeds a force corresponding to the pressure in the primarypressure chamber i while the primary pressure is lower than apredetermined level. Consequently, an A valve element 24 included in theA valve is at its open position and a B valve element 25 included in theB valve is at its closed position, the pressure in a main valve drivingpressure chamber d is equal to the primary pressure, a main valveelement 5 is at its closed position, and a sealing member 5 s attachedto the main valve element 5 and a sealing member attached to the B valveelement 25 form sealed joints.

When the primary pressure rises above the predetermined level, thepressure in the primary pressure chamber i rises, the forcecorresponding to the pressure in the primary pressure chamber i exceedsthe force of the spring 27. Consequently, the A valve element 24 ismoved to its closed position, the B valve element 25 is moved to itsopen position, and the pressure in the main valve driving pressurechamber d decreases toward the secondary pressure. Therefore, the mainvalve element 5 is moved to its open position to discharge the liquid,so that the rise of the primary pressure is suppressed. Thus, the valveapparatus serves as a safety valve.

If the main valve unit needs to be opened forcibly for open discharging,a valve may be interposed between connecting passages m and q or betweenan inlet passage a and an outlet passage c, and the valve may be opened.

A valve apparatus in a twenty-first embodiment of the present inventionshown in FIG. 21 is similar to the valve apparatus in the twentiethembodiment and is provided with a pilot valve unit different from thatof the valve apparatus in the twentieth embodiment. As shown in FIG. 21,an A valve element 24 and a B valve element 25 are placed in anintermediate chamber g. Although the arrangement of connecting passagesin the twenty-first embodiment is somewhat different from that of thecorresponding connecting passages in the twentieth embodiment becausethe valve apparatus in the twenty-first embodiment is a modification ofthe valve apparatus in the twentieth embodiment, the valve apparatus inthe twenty-first embodiment is similar in other respects, functions andeffects to that in the twentieth embodiment and hence furtherdescription thereof will be omitted.

A valve apparatus in a twenty-second embodiment of the present inventionshown in FIG. 22 is formed by containing any one of the valveapparatuses in the foregoing embodiments in a case 61. A valve apparatusshown in FIG. 22 employs the valve apparatus in the first embodiment byway of example. Any one of the valve apparatuses in the foregoingembodiments may be employed. The case 61 is provided with flanges orthreaded openings to be connected to external conduits. The valveapparatus can easily be installed in the ground without requiring workfor forming a pit, which saves time and costs of construction work. Thecase 61 may be of any suitable shape and of any suitable material; thecase 61 may be a rectangular box or a cylindrical box and may be made ofa steel, concrete, an FRP or a reinforced plastic material.

Technical features common to the foregoing embodiments will be describedbelow.

In the pilot valve units of all the embodiments, the A valve element 24and the B valve element 25 are formed integrally with the spool and movetogether, the primary pressure and the secondary pressure is combined inthe pilot valve unit to produce a combined pressure, the combinedpressure is applied to the main valve driving pressure chamber d torespond quickly to the variation of the condition of flow. The valveapparatus operates quickly. Since the valve elements 24 and 25 areformed and arranged so as to create a state where one of the valveelements 24 and 25 is at its open position while the other is at itsclosed position, and a state where both the valve elements 24 and 25 aresubstantially at their closed positions when the flow is stable,chattering and hunting scarcely occur. As mentioned in the descriptionof some of the embodiments, both the valve elements 24 and 25 can beplaced in the intermediate chamber g. The valve elements 24 and 25 maybe formed with separate spools, respectively. The disposition(positional relation) and the combination of the chambers f, g, h, i, j,k, v and w, and the arrangement of the connecting passages may bechanged within the scope of the present invention, and the constructionof the pilot valve unit is not limited to those of the pilot valve unitsemployed in the embodiments specifically described herein.

The fixed-pressure applying means included in the pilot valve unit maybe an elastic member other than the spring employed in the foregoingembodiments, a combination of a weight and a linkage, a mechanismcapable of multiplying force, a pneumatic mechanism or a hydraulicmechanism.

Although the main valve unit provided with the main valve element 5employed in each of the foregoing embodiments is a lift valve, the mainvalve unit may be a valve unit other than the lift valve, such as abutterfly valve, a gate valve, a ball valve or such. As mentioned in thedescription of some of the embodiments, the main valve element 5 may beformed integrally with the main valve driving member 6. In the foregoingembodiments, the main passage extending through the inlet passage a→ themain valve opening b→ the outlet passage c, and the main valve drivingpressure chamber d are formed in the main valve casing 1 to form themain valve unit in a simple construction. However, the main passage andthe main valve driving pressure chamber d may be formed in two separatevalve casings, respectively, and the main valve element 5 and the mainvalve driving member 6 may be fixed to the opposite end parts of a mainvalve stem extending through the two valve casings.

Some cases require that the main valve unit operates gradually toprevent the influence of pressure pulsation resulting from the variationof flow, such as chattering and hunting. Such a requirement may be metby forming the main valve opening b in a saw-toothed shape to make flowrate vary smoothly, by providing the main valve unit with a dampingdevice 8 (damper) comprising a cylinder and a piston or by providing themain valve driving member 6 with a damping device 8 (damper). The pilotvalve unit may be provided with a damping device or some of theconnecting passages may be provided with a restrictor. Those dampingmeans for making the main valve unit operate gradually may be usedindividually or some of those damping means may be used in combinationor the valve apparatus need not be provided with any one of thosedamping means when unnecessary.

The variable restrictor (or the orifice) 11 for constant-flow controlfunction may be a generally known valve, such as a butterfly valve, agate valve, a ball valve or a lift valve. The restrictor 11 may bemanually operated or may be operated automatically by a suitableactuator. As mentioned in the description of some of the embodiments therestrictor (or the orifice) 11 may be disposed on either the upstreamside or the downstream side of the main valve unit. When an adjustingdevice (adjusting screw 28) is combined with the fixed-pressure applyingmeans (spring 27) of the pilot valve unit, a flow rate setting operationby using the restrictor (orifice) 11 is not necessarily necessarybecause a desired flow rate can be set by adjusting the fixed-pressureapplying means, and hence the fixed orifice plate 11 may be used insteadof the variable restrictor 11. Needless to say, it is desirable that thefixed orifice plate is replaceable.

The float valves 30, 36 and 37 for a liquid level control function maybe any suitable well-known valves including ball taps. Valves operatedby a liquid level sensor may be used instead of the float valves. Eachof the float valves 30, 36 and 37 may be placed at the free end part ofthe connecting passage to discharge the liquid into the downstream sideof the main valve unit or may be placed as middle part of the connectingpassage depending on the condition of the site where the valve apparatusis installed.

The sealing members mounted on the component parts required to form asealed joint may be O rings, sealing rings, a diaphragm, a bellows orsuch. If those component members are able to form a satisfactory sealedjoint by directly coming into contact with the corresponding componentmember, the sealing member may be omitted. Naturally, comblikeprojections or a honeycomb structure may be formed in a parts of thevalve apparatus through which rapid currents are expected to flow toprevent cavitation or the like.

There is no particular restriction on the application of conventionaltechniques to the component members of the valve apparatus in accordancewith the present invention. Various changes and variations may be madein the foregoing embodiments without departing from the scope of theinvention and the present invention is not limited in practicalapplication to the embodiments specifically described herein.

Industrial Applicability

The automatic regulating valve apparatus in accordance with the presentinvention provided with the pilot valve unit based on a novel technicalidea is capable of being easily formed in large size or high-pressuretype, which has been difficult in the conventional direct-actingautomatic regulating valve apparatus. The automatic regulating valveapparatus in accordance with the present invention is capable ofexercising excellent automatic control functions including aconstant-flow control function, an emergency shutoff function, a liquidlevel control function and an upstream pressure control function, has aperfect sealing function. Since the pilot valve unit is not providedwith any fixed restricting passage, such as a needle valve, and capableof exercising a clogging preventing function achieved by self-cleaningoperation, the automatic regulating valve apparatus is maintenance-free.Although the automatic regulating valve apparatus operates quickly,chattering and hunting rarely occur. The main valve unit and the pilotvalve unit of the automatic regulating valve apparatus are simple inconstruction and easily adjustable. The automatic regulating valveapparatus does not have any component parts which are difficult todesign, manufacture, operate, maintain and manage, and hence theautomatic regulating valve apparatus is highly reliable and economicallyeffective.

What is claimed is:
 1. An automatic regulating valve apparatuscomprising: a main valve unit and a pilot valve unit operativelyconnected to the main valve unit to control the main valve unit, whereinthe main valve unit comprises a main valve casing, a main valve elementdisposed in the main valve casing, and a main valve driving memberdisposed in the main valve casing together with the main valve elementand having a pressure receiving area greater than that of the main valveelement, the main valve element is disposed on an upstream side of avalve seat so as to form a restricting passage between the main valveelement and the main valve seat, the main valve driving member isdisposed for sliding movement in a space defined by a cylindrical wallformed in the main valve casing so as to define a main valve drivingpressure chamber together with the cylindrical wall, a restrictor isdisposed in a passage extending through the main valve unit; the pilotvalve unit comprises a pilot valve A and a pilot valve B which areoperated by a balance of counteracting forces respectively produced by apressure difference across the restrictor and a fixed-pressure applyingmember, the pilot valve A opens when the pressure difference across therestrictor rises above a predetermined level and closes when the samedrops below the predetermined level, the pilot valve B closes when thepressure difference across the restrictor rises above the predeterminedlevel and opens when the same drops below the predetermined level; andthe pilot valve A and the pilot valve B are arranged in series andconnected between the upstream and the downstream side of the main valveunit by connecting passages with a chamber between the pilot valves Aand B connected to the main valve driving pressure chamber; and whereina valve element is further provided, said valve element being capable ofclosing when liquid level on the downstream side of the main valve unitrises above a predetermined level and of opening when the same fallsbelow the predetermined level, and placed in series in a connectingpassage connected to the pilot valve B.
 2. The automatic regulatingvalve apparatus according to claim 1, wherein the restrictor is of avariable type.
 3. An automatic regulating valve apparatus comprising: amain valve unit and a pilot valve unit operatively connected to the mainvalve unit to control the main valve unit, wherein the main valve unitcomprises a main valve casing, a main valve element disposed in the mainvalve casing, and a main valve driving member disposed in the main valvecasing together with the main valve element and having a pressurereceiving area greater than that of the main valve element, the mainvalve element is disposed on an upstream side of a valve seat so as toform a restricting passage between the main valve element and the mainvalve seat, the main valve driving member is disposed for slidingmovement in a space defined by a cylindrical wall formed in the mainvalve casing so as to define a main valve driving pressure chambertogether with the cylindrical wall, a restrictor is disposed in apassage extending through the main valve unit; the pilot valve unitcomprises a pilot valve A and a pilot valve B which are operated by abalance of counteracting forces respectively produced by a pressuredifference across the restrictor and a fixed-pressure applying member,the pilot valve A opens when the pressure difference across therestrictor rises above a predetermined level and closes when the samedrops below the predetermined level, the pilot valve B closes when thepressure difference across the restrictor rises above the predeterminedlevel and opens when the same drops below the predetermined level; andthe pilot valve A and the pilot valve B are arranged in series andconnected between the upstream and the downstream side of the main valveunit by connecting passages with a chamber between the pilot valves Aand B connected to the main valve driving pressure chamber; and whereina valve element is further provided, said valve element being capable ofclosing when liquid level on the downstream side of the main valve unitrises above a predetermined upper limit and of opening when the samefalls below the predetermined lower limit, and placed in series in aconnecting passage connected to the pilot valve B.
 4. An automaticregulating valve apparatus comprising: a main valve unit and a pilotvalve unit operatively connected to the main valve unit to control themain valve unit, wherein the main valve unit comprises a main valvecasing, a main valve element disposed in the main valve casing, and amain valve driving member disposed in the main valve casing togetherwith the main valve element and having a pressure receiving area greaterthan that of the main valve element, the main valve element is disposedon an upstream side of a valve seat so as to form a restricting passagebetween the main valve element and the main valve seat, the main valvedriving member is disposed for sliding movement in a space defined by acylindrical wall formed in the main valve casing so as to define a mainvalve driving pressure chamber together with the cylindrical wall, arestrictor is disposed in a passage extending through the main valveunit; the pilot valve unit comprises a pilot valve A and a pilot valve Bwhich are operated by a balance of counteracting forces respectivelyproduced by a pressure difference across the restrictor and afixed-pressure applying member, the pilot valve A opens when thepressure difference across the restrictor rises above a predeterminedlevel and closes when the same drops below the predetermined level, thepilot valve B closes when the pressure difference across the restrictorrises above the predetermined level and opens when the same drops belowthe predetermined level; and the pilot valve A and the pilot valve B arearranged in series and connected between the upstream and the downstreamside of the main valve unit by connecting passages with a chamberbetween the pilot valves A and B connected to the main valve drivingpressure chamber; and wherein a pilot valve C is further provided, saidvalve C being operated by a balance of counteracting forces respectivelyproduced by a pressure difference across the main valve unit and a fixedpressure applying element, capable of closing when the pressuredifference across the main valve unit rises above a predetermined leveland of opening when the same drops below the predetermined level; afirst float valve capable of closing when liquid level on the downstreamside of the main valve unit rises above a predetermined upper limit andof opening when the same drops below the predetermined upper limit; anda second float valve capable of closing when the liquid level on thedownstream side of the main valve unit rises above a predetermined lowerlimit and of opening when the same drops below the lower limit; andwherein the pilot valve C and the first float valve are placed in seriesin a connecting passage connected to the pilot valve B, and the mainvalve driving pressure chamber is connected through the second floatvalve to the downstream side of the main valve unit.
 5. An automaticregulating valve apparatus comprising: a main valve unit and a pilotvalve unit operatively connected to the main valve unit to control themain valve unit, wherein the main valve unit comprises a main valvecasing, a main valve element disposed in the main valve casing, and amain valve driving member disposed in the main valve casing togetherwith the main valve element and having a pressure receiving area greaterthan that of the main valve element, the main valve element is disposedon an upstream side of a valve seat so as to form a restricting passagebetween the main valve element and the main valve seat, the main valvedriving member is disposed for sliding movement in a space defined by acylindrical wall formed in the main valve casing so as to define a mainvalve driving pressure chamber together with the cylindrical wall, arestrictor is disposed in a passage extending through the main valveunit; the pilot valve unit comprises a pilot valve A and a pilot valve Bwhich are operated by a balance of counteracting forces respectivelyproduced by a pressure difference across the restrictor and afixed-pressure applying member, the pilot valve A opens when thepressure difference across the restrictor rises above a predeterminedlevel and closes when the same drops below the predetermined level, thepilot valve B closes when the pressure difference across the restrictorrises above the predetermined level and opens when the same drops belowthe predetermined level; and the pilot valve A and the pilot valve B arearranged in series and connected between the upstream and the downstreamside of the main valve unit by connecting passages with a chamberbetween the pilot valves A and B connected to the main valve drivingpressure chamber; and wherein a pilot valve D is further provided, saidvalve D being operated by a balance of counteracting forces respectivelyproduced by a pressure difference across the restrictor and a fixedpressure applying element, capable of opening when the pressuredifference across the restrictor rises above a predetermined level andof closing when the same drops below the predetermined level; a firstfloat valve capable of closing when liquid level on the downstream sideof the main valve unit rises above a predetermined upper limit and ofopening when the same drops below the predetermined upper limit; and asecond float valve capable of closing when the liquid level on thedownstream side of the main valve unit rises above a predetermined lowerlimit and of opening when the same drops below the lower limit; whereinthe pilot valve D and the first float valve are placed in series in aconnecting passage connected to the pilot valve B, and the main valvedriving pressure chamber is connected through the second float valve tothe downstream side of the main valve unit.
 6. The automatic regulatingvalve apparatus according to claim 5, wherein three valve elements ofthe pilot valves A, B and D are disposed coaxially so as to movetogether according to the balance of the counteracting forces producedby the pressure difference across the restrictor and the fixed-pressureapplying means.
 7. An automatic regulating valve apparatus comprising amain valve unit and a pilot valve unit operatively connected to the mainvalve unit to control the main valve unit; wherein the main valve unitcomprises a main valve casing, a main valve element disposed in the mainvalve casing, and a main valve driving member disposed in the main valvecasing together with the main valve element and having a pressurereceiving area greater than that of the main valve element, the mainvalve element is disposed on an upstream side of a valve seat so as toform a restricting passage between the main valve element and the mainvalve seat, the main valve driving member is disposed for slidingmovement in a space defined by a cylindrical wall formed in the mainvalve casing so as to define a main valve driving pressure chambertogether with the cylindrical wall; the pilot valve unit comprises apilot valve A and a pilot valve B operated by a balance of counteractingforces respectively produced by a pressure difference across the mainvalve unit and a fixed-pressure applying means, the pilot valve A iscapable of opening when the pressure difference across the main valveunit rises above a predetermined level and of closing when the samedrops below the predetermined level, the pilot valve B is capable ofclosing when the pressure difference across the main valve unit risesabove the predetermined level and of opening when the same drops belowthe predetermined level, the pilot valves A and B are arranged in seriesand connected between the upstream and the downstream side of the mainvalve unit by connecting passages with a chamber between the pilotvalves A and B connected to the main valve driving pressure chamber; afirst float valve capable of closing when liquid level on the downstreamside of the main valve unit rises above a predetermined upper limit andof opening when the same drops below the predetermined upper limit, anda second float valve capable of closing when the liquid level on adownstream side of the main valve unit rises above a predetermined lowerlimit and of opening when the same drops below the lower limit areemployed; and the first float valve is placed in series in a connectingpassage, connected to the pilot valve B, and the main valve drivingpressure chamber is connected through the second float valve to thedownstream side of the main valve unit.